"All hyperbole aside, this hearing is about nothing less than the future of the Internet and, significantly, who has the right, the ability and the authority to determine it," said Representative Bob Goodlatte, a Virginia Republican. "Should it be decided by a few people in Washington, Beijing, Moscow, Sao Paolo or even Silicon Valley or should it be determined by those who use and stand to benefit from it?"

Goodlatte suggested that other countries would try to control ICANN after the U.S. ends its contract. The U.S. can "rightly take credit for the freedom that exists the Internet today," he said during a hearing. "When we let go of that final link, will that institution be safer from those efforts to regulate the Internet, or will it be more exposed because it no longer has the protection of the United States?"

The Internet engineers, companies and civil society groups involved in ICANN wouldn't allow a government takeover of the organization, supporters of the NTIA's plan said. "I cannot imagine the Internet engineers that I know agreeing to do any of the parade of horribles that people are concerned about," said Representative Zoe Lofgren, a California Democrat.

Separately, the technology subcommittee of the House Energy and Commerce Committee voted Thursday to approve the Domain Openness Through Continued Oversight Matters (DOTCOM) Act, which would require a U.S. Government Accountability Office study about the effects of the transition before it happens. Members of that committee raised similar concerns in a hearing last week.

President Barack Obama's administration opposes the bill because it raises questions about the U.S. government's long-term support of a multistakeholder governance model at ICANN, said NTIA Administrator Larry Strickling.

Strickling assured Judiciary Committee members that the agency would not give up oversight of ICANN unless it is satisfied that the organization has a transition plan in place that prohibits a government takeover.

Several Republicans committee members questioned NTIA's move to end its contractual relationship with ICANN as soon as late 2015, but Strickling defended the plan, saying one of the main reasons for the change is to remove the perception in some countries that the U.S. has too much control.

While the NTIA's contract for ICANN to operate the Internet Assigned Numbers Authority (IANA) functions is largely "symbolic," the move would show the world that the U.S. supports a multistakeholder governance model at ICANN that it has advocated since 1998, Strickling said.

The U.S. government will continue to be an "active and vigorous participant" in ICANN, he said.

Fadi ChehadA(c), ICANN's president and CEO, urged the U.S. government to embrace its long-advocated multistakeholder oversight of ICANN. "This is the time to let go and show the world our trust," he said. "This is the moment the world wants to watch us trust our own model. Let's not show them we don't trust it."

Still, some witnesses at the hearing raised concerns that the end of the IANA contract would remove the last outside oversight of ICANN. Before the transition, ICANN should consider setting up an independent auditor or inspector general, said Paul Rosenzweig, founder of Red Branch Law and Consulting.

Without those outside controls, there's nothing stopping ICANN from changing its own practices and bylaws, he said. "All of the restrictions ... are internal to ICANN," he said. "Times come where people waive those restrictions or change them, or they mutate over time."

Without the NTIA contract, there's no limit on ICANN's ability to raise fees on its domain-name system services, added Daniel Castro, senior analyst at the Information Technology & Innovation Foundation, a tech-focused think tank.

"Without U.S. oversight, ICANN has the potential to grow into the world's largest unregulated monopoly," he said. "We should be very mindful of creating a global organization with little accountability that can effectively tax the Internet."

The participants in ICANN would not allow the organization to become an unregulated monopoly, Strickling countered. That view "totally disregards the presence of hundreds of stakeholders, thousands of stakeholders, who actually set the policies for ICANN," he said. "If you're saying [the groups involved] are all going to allow that to happen, then you're basically saying you don't believe in the multistakeholder model."

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's email address is grant_gross@idg.com.